1. Field of the Invention
This invention relates to brake boosters for vehicles and more particularly to vacuum brake boosters having a master cylinder mounted thereon.
2. Discussion of the Background
A conventional vacuum brake booster has a power piston which is actuated by vacuum pressure which is, in turn, controlled in response to depression force on a brake pedal, and a master cylinder having a primary piston which is actuated in association with movement of the power piston. Since the primary piston of the master cylinder is associated with power piston of the booster, it has been proposed that the master cylinder be directly secured to the body of the brake booster. The thickness of the body may be preferably minimized for the purpose of lightening the weight of the vehicle and, therefore, a reinforcing member 12 may be provided at an inner side portion of the body of the booster in order to increase the strength thereof as shown in FIG. 3. In FIG. 3, reinforcing member 12 is made of metal and is of a doughnut configuration having inner and outer circumference flanges 15, only one of such flanges 15 being shown in FIG. 3. The reinforcing member 12 is arranged between a body 2 of the brake booster and a bolt 13 to install the master cylinder on the body 2 of the brake booster, and a projection 18 of the head of bolt 13 is then welded to the reinforcing member 12 and a projection 20 of the body 2 is welded to the reinforcing member 12. Thus, bolt 13 and reinforcing member 12 are secured to the body 2. However, r.sub.2 is located further outside than the location of R.sub.1 where r.sub.2 is the center of radius R.sub.2 of a bent portion 17 of the body 2 and r.sub.1 is a center of bending radius R.sub.1 of flange 15. Therefore, bent portion 17 of body 2 is spaced from the reinforcing member 12 and thus, only the weld projection 20 of the body 2 is subjected to stress generated about bolt 13 upon operation of the brake and the durability of the body is correspondingly reduced.